The present invention relates to an image recording apparatus and more particularly to an image recording apparatus and method for forming images on a recording medium using toners.
Image recording methods and apparatus for forming images on a recording medium using toners are well known. One of these techniques is to form toner images on a recording medium by supplying electrically conductive, magnetic toners in a gap area between the recording medium and an recording electrode and applying a voltage to the recording electrode. Such a technique is disclosed in U.S. Pat. No. 4,763,143 issued to Ohba et al, U.S. Pat. No. 4,777,499 issued to Okuna et al, JP-A-53-6,043 and JP-A-64-14,050.
The technique of forming images by supplying electrically conductive, magnetic toners in a recording area formed between a recording electrode and a recording medium and applying a voltage corresponding to the image to be recorded results not only in toners being relatively strongly adhered to the recording medium for image formation but also in toners (commonly referred to as `non-image toners`) being relatively weakly deposited thereon. These strongly adhered toners shift downstream due to movement of the recording medium as they are deposited on the recording medium and are duplicated on the recording medium (paper) at a duplication section; however, the latter toners (i.e. the non-image toners) cause background dirt and fog, which deteriorates the image quality. To obviate this, the above prior art intends to remove the unnecessary toners not contributing to image formation from the recording medium and to collect them for subsequent image recording. More specifically, the unnecessary toners, other than the toners relatively strongly adhered to the recording medium for image formation, are removed from the recording medium arranged apart from the recording medium by magnetic means, such as a magnetic brush and a magnetic roll, and are collected in a hopper.
The above technique of collecting unnecessary toners using the magnetic means is preferable to relatively easily lessen the fog and dirt of the image background due to the unnecessary toners.
However, in an actual image recording, it is difficult to completely eliminate fog and background dirt. The strong action of the magnetic field generated by the magnetic means in order to completely eliminate fog and background dirt will remove the toners used for image formation from the recording medium and thus will result in insufficient image density.